Examinations or treatments of an (ill) patient are increasingly carried out in a minimally invasive manner, i.e. with as little operative effort as possible. Examples of such procedures are treatments using endoscopes, laparoscopes, catheters or biopsy needles, which are inserted into the examination area of the patient, subsequently referred to as “region of interest” or “area of interest”, via a small opening in the body in each instance. By way of example, catheters are frequently used within the scope of angiographic or cardiological examinations.
The initial problem from a medical-technology perspective lies in clearly identifying a region of interest (e.g. a tumor), i.e. in recognizing its contours, in a 2D fluoroscopy image, recorded for instance using a conventional x-ray device or using an x-ray C-arm. The present invention concerns the solution to this problem.
The problem described is particularly prominent if the region of interest within the scope of an operation or examination must be approached using a medical instrument. This could conceivably be—without restricting general applicability—a biopsy needle or a catheter which can be visualized precisely and with a high resolution in one or more 2D fluoroscopy images by means of an intraoperative x-ray control, e.g. with the so-called C-arm, but however the representation of the anatomy of the patient, in particular the representation of the pathogenous regions of interest (tumor, aneurism, stenosis etc.) would be inadequate and unsuitable with these types of control recordings to provide the doctor with an orientation aid. Precise localization of the affected area in the body is thus very difficult.
Numerous approaches exist in the prior art to assist the doctor in orientation within the body using intraoperative x-ray control.
The oldest and thus also the best-known method consists in injecting contrast medium, taking an instantaneous x-ray, storing this as a reference image and underlaying a current (intraoperative) fluoroscopy. It is however again disadvantageous that this process must be repeated with each new angulation of the C-arm or other changes in the (angiography) system (e.g. changes by means of zoom, SID—Source Image Distance, table displacement etc.).
A further method consists of first acquiring a volume data set of the relevant body area, which fully includes the region of interest and/or the diseased organ or tissue or organ or tissue to be diagnosed. This is carried out for instance by (contrast medium-based) spiral computer tomography or other 3D imaging modalities. (In MRT recordings, tumors are also visible without contrast medium for instance.) Furthermore, an artificial 3D volume projection image is generated on the basis of the 3D data set, which is to be viewed from the same perspective as the current fluoroscopy image and is also underlaid on this image. Reference is also made in this context to “artificial projection” of the 3D volume.
External (infrared-based, magnetic etc.) navigation systems also exist, which determine the 3D position of a medical instrument (catheter, needle) by means of external position sensors and allow an orientation within a previously recorded volume data set on the basis of this information.
The common factor in all 3D-based methods is a photorealistic underlay of a (3D) reference image relating to a current (intraoperative) fluoroscopy image with the disadvantage of a largely inconcise representation of the anatomy, which unsettles the doctor rather than aids him/her.